高伯羟基含量聚(碳酸酯-醚)多元醇的制备

Synthesis of High Primary Hydroxyl Content Poly(carbonate-ether) Polyol

聚(碳酸酯-醚)多元醇又称二氧化碳基多元醇,是通过CO_2与环氧丙烷(PO)的调聚反应所制备的.由于环氧丙烷开环反应时优先在空间位阻较低的亚甲基上的碳-氧键断裂,生成端羟基以仲羟基为主的二氧化碳基多元醇,其伯羟基含量通常低于20%,导致其与异氰酸酯反应的活性较低.本文提出了环氧乙烷(EO)封端、EO和CO_2共聚封端、一锅法三元调聚封端(PO、EO与CO_2)等3种方法来提高二氧化碳基多元醇中的伯羟基含量.研究表明,利用EO封端方法会导致多元醇中碳酸酯含量的降低,而采用EO和CO_2共聚进行封端可合成出伯羟基含量达72%的二氧化碳基多元醇,且碳酸酯含量下降很少.最后我们利用双金属催化剂(DMC)对PO和EO的开环反应速度的差异,采用一锅法将PO、EO和CO_2进行三元调聚反应,合成了伯羟基含量可达62%的二氧化碳基多元醇,且碳酸酯含量几乎不受影响.

During the past decade,poly(carbonate-ether)polyols,also known as CO2-polyols,have been synthesized by the copolymerization of CO2 and propylene oxide(PO)with double metal cyanide(DMC)catalyst in the presence of various chain transfer agents.CO2-polyols show great potential as substitutes for polyols derived from fossil feedstock in the polyurethane industry.However,the ring opening reaction of PO generally occurs at the methylene carbon-oxygen bond due to less steric hindrance producing CO2-polyol mainly with the second hydroxyl(2°OH)as terminal group,therefore,the terminal primary hydroxyl(1°OH)content is usually lower than 20%,which leads to their much lower reactivity with isocyanate.Three methods were chosen for increasing the primary hydroxyl content of CO2-polyols,including ethylene oxide(EO)end-capping,copolymerization end-capping of EO and CO2,and one-pot ternary polymerization(PO,EO and CO2)endcapping.The primary hydroxyl content of the polyols was analysed based on the difference in 19 F-NMR chemical shifts between the primary and secondary trifluoroacetyl esters of the polyols.19 F-NMR and 1 H-NMR spectroscopy indicated that EO end-capping could improve the 1°OH content of CO2 polyols in some extent,while accompanied with obvious loss of the carbonate unit content.Therefore,the EO end-capping method can only provide polyols with low carbonate unit content.Yet CO2-polyols with 72%of 1°OH content have been synthesized by copolymerization end-capping of EO and CO2,and the content of carbonate unit decreases little.Finally,taking advantage of the different reactivity of PO and EO with double metal cyanide catalysts(DMC),we synthesized CO2-polyols with 62%of 1°OH content by one-pot ternary polymerization of PO,EO and CO2,and the carbonate unit content was almost unaffected.This strategy provides a safe and efficient possibility to synthesize high 1°OH content CO2-polyols.